The invention relates to an apparatus for folding and closing the tops of folding cartons which are prefabricated from cut boxboard stock having an inner thermoplastic-resin liner, and in particular a liner with a composite structure of thermoplastic-resin layer/aluminum foil/thermoplastic-resin layer, comprising a folding station, a pressing and ultrasonic welding station, and conveying means which carries the folding cartons in a row, upright, to the folding station and to the pressing/welding station.
In a prior-art apparatus of this type, the top of every folding carton is so folded in a first station that the fillet seam is parallel to the direction of travel. The folding carton then leaves this folding station and reaches the pressing/welding station as such. On the way to the latter, the folded top is held in that position by guide rails which laterally engage the fillet seam. The tools are constructed as an anvil and ultrasonic welding horn, whereby the inner liner of thermoplastic resin is heated and the tools also serve to press the fillet-seam areas to be welded together during the sealing operation and, following the latter, to hold them together for a certain cooling-off period. To this end, both the anvil and the ultrasonic welding horn are provided with flat contact surfaces.